1. Field of the Invention
This invention relates generally to heating apparatus, and more particularly to a method and apparatus utilizing submerged products of combustion for heating liquids.
2. Brief Description of the Prior Art
Northcott, U.S. Pat. No. 2,900,975 discloses a submerged heating apparatus in which a substantial portion of the combustion zone extends below the liquid level of the material to be heated and wherein the entire burner mechanism and combustion zones are situated within the container holding the liquid to be heated.
Ohara et al, U.S. Pat. No. 3,882,844 discloses a submerged hot gas heat exchanger having a combustion gas sparge pipe with delivery ports along its upper surface, vertical fins connected to the outer surface of each heat exchanger tube, and a process liquid inlet header tank provided as a double tube structure. Baffle plates are provided in each of the tubes in the process liquid evaporating zone.
Luring et al, U.S. Pat. No. 3,060,921 discloses water heater employing the concept of submerged combustion wherein gaseous products of combustion are discharged below the surface of a primary body of water transferring heat by direct mixing. The water which is to be heated and used is circulated through the primary water in indirect thermal contact therewith to be heated by the primary water.
Brock, U.S. Pat. No. 3,568,658 discloses a water heater comprising a tank, a burner can in the tank, water inlet means at the upper portion of the burner can for flowing water thereinto, gas injection means communicating with the upper portion of the burner can for introducing a fuel/air mixture to the burner can, and fluid extraction means communicating with the lower portion of the burner can for evacuating gases and water therefrom. The gases and water extracted from the burner can are injected back into the water of the tank, and the gases bubble up through the water.
Wyatt, U.S. Pat. No. 4,441,460 discloses a method and apparatus for heating fluids by the use of vapor generators in which a fuel/air mixture is burned in the presence of a stream of feed water to produce a stream of steam and non-condensibles which is then heat exchanged with stream of fluid to be heated.
Goodnight et al, U.S. Pat. No. 4,237,858 discloses a gas burner system having a first air supply plenum which is spaced above a second plenum or combustion chamber. A burner is positioned at the inlet to the combustion chamber. Water surrounds the combustion chamber plenum and the side walls around the burner which is used for heating and evaporation.
Santoleri et al, U.S. Pat. No. 3,368,548 discloses a submerged hot gas heat exchanger which includes a tank containing a heat transfer liquid, a plurality of burners surrounded by a shroud depending downwardly into the tank, a weir surrounding the shroud to direct hot gas from the burner outwardly at the bottom of the tank into the liquid, and a plurality of tubes within the tank through which the liquid to be heated an converted into a gaseous state is caused to pass.
Durrenberger, U.S. Pat. No. 4,685,444 discloses a process and equipment for heating a liquid comprising a tank partially filled with water containing an absorbent mixed therein and a tube coil submerged in the water in the tank through which the water to be heated and utilized is conduct ed. A burner is contained in a cylindrical flame tube which extends downwardly into the tank an into the water. Surface area enlarging parts such as Raschig rings may be incorporated into the flame tube between the burner and lower portion of the tube. A rotor is positioned within the lower portion of the flame tube and connected to a motor. The burner produces a flame inside the flame tube and suction is created by the rotor and the combustion gases are drawn into the water in the form of bubbles. The flame gases are precooled by conducting the absorbent liquid from the area in the vicinity of the rotor to the top portion of the flame tube s that the absorbent liquid continuously wets and cools the outer wall of the tube. As the rotor turns, the liquid in the tank rises to enter bores in the flame tube side wall and wets the Raschig rings whereby additional cooling is achieved.
The present invention is distinguished over the prior art in general, and these patents in particular by apparatus for heating a liquid by mixing combustion products therewith. The apparatus comprises a housing having a liquid-containing reservoir compartment, a mixing chamber above the reservoir which contains a tortuous fluid flow path, a combustion chamber above the mixing chamber containing a gas burner and including means for igniting and burning a mixture of air and fuel therein and an apertured water jacket at the upper end thereof. A pump draws liquid from the reservoir and discharges it through the water jacket onto the combustion chamber side wall to cool the burning mixture. The discharged liquid is collected at the lower end of the combustion chamber and distributed evenly throughout the tortuous fluid flow path in said mixing chamber to thoroughly mix the hot combustion gases with the hot liquid mixture for maximum heat transfer. After mixing, the mixture falls through an air space back into the reservoir to separate the excess gases from the mixture which are vented to atmosphere. The heated liquid may be recycled through a hot water supply piping system for industrial usage. A coil submerged in the reservoir allows a second liquid to be heated thereby for use in a hot water supply system for residential or industrial usage. A second coil installed in the combustion chamber and coupled to the lower coil allows higher temperatures to be achieved.